Two types of conditional cell division mutants of Escherichia coli will be used to attempt to determine how completion of rounds of DNA replication initiate subsequent cell division. Temperature-sensitive mutants which do not form septa at high temperature and lon mutants which do not form septa after temporary periods of DNA synthesis inhibition will be studied. Complementation and fine structure mapping will be used to define the genes genetically. Biochemical studies will include detection and assay of the cell division gene products. BIBLIOGRAPHIC REFERENCES: Walker, J. R., A. Kovarik, J. S. Allen, and R. A. Gustafson. Regulation of Bacterial Cell Division: Temperature-Sensitive Mutants of Escherichia coli That Are Defective in Septum Formation. J. Bacteriol. 123 (1975) 693-703. Walker, J. R., and A. Kovarik. Strain-Specific Difference That Affects the Inhibition of Division of Escherichia coli Filaments by Chloramphenicol. J. Bacteriol. 123 (1975) 752-754.